The present invention relates to a method for imaging lymphatic structures and to a kit suitable for use therefor.
There is a need, particularly in oncology, for a method that clearly delineates lymphatic structures. Lymphatic structures, particularly lymph nodes, drain tissue and extravascular regions of various molecular and macromolecular substances, including antigens, infectious agents, and cells, serving as a filter as well as a part of the host organism's immunological apparatus. It is well known that certain substances with appropriate physical properties, when injected into a suitable tissue plane, are transported from the injection site by a drainage system and sequestered in regional and then more distant lymph nodes. Some of these substances, particularly colloids, are passively retained in sinusoids and actively phagocytosed by the reticuloenothelial (RE) cells within the lymph node. When a radioisotope is incorporated in such a pharmaceutical suitable for lymphatic accretion, the lymph system, particularly the draining lymph nodes, can be imaged with a suitable scintigraphic system.
However, when a disease process impacts upon these lymphatic structures, the image of the lymph nodes may be affected in such a manner that their form and appearance is different. For example, a cancer infiltrating a lymph node may replace a large enough portion of the RE tissue in the node to exclude an imaging agent, e.g., a radiocolloid, from that area of the node, resulting in a "negative" image effect. Similar results may be obtained when the lymph node structure and function is compromised by infectious agents, e.g., bacteria, fungi, parasites and viruses.
However, the use of such lymphoscintigraphic methods can present problems in diagnostic interpretation, since "absent" lymph nodes or "decreased uptake of radioactivity" are not in themselves diagnostic of neoplastic or other involvement of the lymph nodes. Moreover, there may be lymph nodes that appear normal in the lymphoscintigram, or even show increased radiocolloid uptake, when these nodes are found to have metastases upon microscopic examination. Conversely, nodes with no apparent metastatic involvement may show decreased or no radiocolloid uptake. Thus, a method with greater specificity for lymph node involvement in cancer or in infectious diseases would be of considerable diagnostic value.
Methods of localization and therapy of tumors and infectious lesions using labeled antibodies and antibody fragments which specifically bind markers produced by or associated with tumors or infectious lesions have been disclosed, inter alia, in Hansen et al., U.S. Pat. No. 3,927,193 and Goldenberg, U.S. Pat. Nos. 4,331,647, 4,348,376, 4,361,544, 4,468,457, 4,444,744, 4,460,459 and 4,460,561, and in related pending applications U.S. Ser. Nos. 609,607 and 633,999, the disclosures of all of which are incorporated herein in their entireties by reference. See also DeLand et al., J. Nucl. Med., 20, 1243-50(1979).
These methods use radiolabeled antibodies which specifically bind to markers produced by or associated with tumors or infectious lesions, and result in a "positive" image, i.e., uptake of radioactivity attached to the antibody in the structure involved with tumor or infectious lesion and having the appropriate antibody target, thus permitting a visualization of the involved structure. Further improvements in the specificity and resolution of these methods is achieved by the use of various substraction techniques which are also disclosed in the aforementioned references, and which enable background, non-specific radioactivity to be distinguished from specific uptake by the tumor or lesion.
Others have employed lymphoscintigraphy to study various types of cancers, using various imaging agents. Current lymphoscintigraphic methods employ Tc-99m antimony sulfide colloid (Tc-ASC) as the imaging agent of choice, although Tc-99m stannous phytate has also been reported as useful. See, e.g., Ege et al., Brit. J. Radiol., 52, 124-9(1979); and Kaplan et al., J. Nucl. Med., 20, 933-7(1979). Earlier, Au-198 colloid was used, as reported by, e.g., Hultborn et al., Acta Radiol., 43, 52(1955); Turner-Warwick, Brit. J. Surg., 46, 574(1959); Vendrell-Torne et al., J. Nucl. Med., 13, 801 (1972); Robinson et al., Surg. Forum, 28, 147 (1977); Sherman et al., Am. J. Roentgenol., 64, 75(1950); and Rosse et al., Minerva Med., 57, 1151 (1966). Intraperitioneal autologous Tc-99m-labeled erythrocytcs were used in mediastinal lymphoscintigraphy to study ovarian cancer by Kaplan et al., Br. J. Radiol., 54, 126(1981). Tc-99m-labeled liposomes were used in axillary lymphoscintigraphy of breast cancer by Osborne et al., Int. J. Nucl. Med. Biol., 6, 75(1979). Tc-99m rhenium sulfide colloid was used in breast cancer lymphoscintigraphy by Gabelle et al., Nouv. Presse Med., 10, 3067(1981). The use of Tc-ASC for lymphoscintigraphic imaging of mammary and prostatic cancers, as well as for malignant melanoma, has been reported by, e.g., Ege, Sem. Nucl. Med., 13, 26(11983); Ege, J. Urol., 127, 265-9 (1982); and Sullivan et al., Am. J. Radiol., 137, 847-51(1981).
DeLand et al., Cancer Res., 40, 2997-3001 (1980), disclose a scintigraphic imaging method using anti-carcinoembryonic antigen antibodies labeled with T-131. They found that the tumor marker, carcinoembryonic antigen (CEA), was accumulated in lymph node metastases and also in some non-metastatic lymph nodes in the drainage path of proximal tumors, and was revealed by binding to labeled antibody.
Lymph nodes have been imaged by magnetic resonance imaging techniques, but not with the use of image enhancing contrast agents, and not with antibody-conjugated imaging agents.
It is important in certain clinical situations to detect the presence or absence of a particular organ, such as the ovary. Moreover, it is often necessary to determine whether an organ is anatomically correct and whether it has pathology, e.g., obstruction, infection, neoplasia and the like, by a non-invasive technique. It would be desirable to have an organ imaging method using organ-specific imaging agents that would make it possible to obtain a "positive" image of the organ, when normal, and a defect in organ visualization if pathology is present. Such a method would provide a new approach to scintigraphic and magnetic resonance imaging of organs and tissues in the body based upon their immunological specificity.
Antibody conjugates comprising organ-specific and tissue-specific antibodies and addends for scintigraphic detection or magnetic resonance image enhancement have not been used as organ imaging reagents.
A need continues to exist for lymphographic imaging methods which are more sensitive and specific for tumor and infectious lesion involvement in lymphatic structures, and for organ imaging reagents and methods with high specificity for differentiation of particular organs and tissues from surrounding structures.